Sutures are used for a variety of surgical purposes, such as approximation of tissue and ligation of tissue. When placing sutures, the strand of suture material to be used typically has a needle affixed to one end which is passed (looped) through the tissue to be approximated or ligated, forming a stitch. The stitch is then tensioned appropriately, and the two free ends of the suture loop, the needle end and the non-needle end, are knotted to retain the desired tension in the stitch. Forming knots in suture during open surgery is a simple matter, though time-consuming, but forming knots in sutures during endoscopic surgery can require two surgeons to cooperate in a multi-step process which is performed with multiple instruments to pass the needle and suture back and forth to tie the suture knot.
Within the prior art there exists a need for devices and methods that reduce the time required to secure a heart valve repair prosthesis in place. To repair or replace a defective valve, clinicians can perform traditional open heart surgery or can utilize a minimally invasive or transcatheter technique. Traditional open heart surgery involves administering anesthesia and putting a patient on cardio-pulmonary bypass. A clinician cuts open the chest to access the heart, and then typically excises the defective native valve leaflets leaving the annulus in place. The clinician places sutures in the annulus or other tissue near the heart valve, and threads the free ends of each loop of the sutures through a sewing cuff on the heart valve prosthesis. The heart valve is then “parachuted” into place by sliding it down the suture free ends until it rests on the annulus. The free ends of each suture loop are tied together on the proximal side of the heart valve with multiple knots to prevent the sutures from backing out. Normally, this process entails about 5-10 knots on each of the 12-20 sutures used per implant, which lengthens the time a patient is on cardio-pulmonary bypass and under anesthesia. There is a direct correlation between time spent on bypass and poor outcomes, and thus any reduction in surgical time that a patient undergoes would be beneficial. Implantation of an annuloplasty ring follows a similar procedure except that the native valve is typically left in place. The annuloplasty ring is sutured in place to reshape or repair the valve annulus and improve native heart valve leaflet coaptation.
There also exists a need to make it easier to secure a heart valve repair prosthesis in place. Currently, a clinician must work in the limited space near the heart to tie knots in sutures. This is a cumbersome process that benefits from a clinician of great dexterity and patience. In a minimally invasive surgery the clinician must use tools that can be passed through a small incision, thus making the tying of knots even more difficult. To implant the prosthesis, a clinician makes a small incision in the chest and uses special tools to pass the heart valve repair prosthesis through the incision. An example of a minimally invasive heart valve repair procedure is transapical aortic valve replacement.
Suture locking devices that eliminate the need to tie knots in order to speed up heart valve replacement are known, as are suture locking devices in general. Suture retainers or locks are used in place of suture knots to prevent passage of a suture end into and through tissue and to maintain the tension applied to the suture material during the suturing procedure. Suture clips and other suture retainers are described in the following publications: U.S. Pat. Nos. 6,066,160, 6,475,230, 7,862,584, 7,875,056, 8,100,923, and 8,105,355.
Despite the existence of knotless suture locking devices in the art, there is a need for improved devices that enable accurate tensioning of the suture and are simple to use. Some of the prior devices utilize a wedge-type system in which a wedge or opposed wedge surfaces are brought together to clamp on the suture. Some of these devices are susceptible to changes in the magnitude of tension in the suture as they are being locked, either loosening or tightening the suture, while others may work loose if there is no additional mechanism to hold them in place. Some devices such as U.S. Pat. No. 7,862,584 utilize a clamping system having a tortuous path for the suture, which are difficult to thread and also may work loose. Another type of suture locking device shown in U.S. Pat. No. 7,235,086 makes use of a plastically deformable member to capture the suture therein. This device depends on accurate deformation of the clamping member, which might permit the suture to slip loose if insufficiently deformed.